1. Field of the Invention
The present invention relates to adjustably limiting pivotal movement between pivotally connected members. More specifically, this invention relates to an adjustable stop for limiting steering angle on vehicles and, in particular, tractors.
2. Description of the Prior Art
On most vehicles, pivotal movement of the steerable wheels or steering angle is limited in some manner to prevent contact between the wheels and other parts of the vehicle. Preventing contact between the moving wheels and other parts of the vehicle such as the frame or body avoids damage to the vehicle wheels or other parts of the vehicle. For most vehicles, the wheel spacing and tire size remains essentially constant and a permanent stop may be incorporated into the design of the vehicle to limit the steering angle of the steerable wheel and avoid the aforementioned contact. However, in vehicles that have adjustable axles variable tire widths or variable chassis dimensions, a permanent or nonadjustable stop may not prevent vehicle and wheel contact for all tire size or tread width combinations without unduly limiting the steering angle for some combinations. Accordingly, it is necessary to provide adjustable limit stops to allow full use of the available steering angle for different tread width and tire combinations.
Agricultural tractors fall into the class of vehicles wherein adjustment to the steering stops is frequently necessary. Wheel spacing is often varied on such tractors by the use of different rim arrangements or variations in axle width. Variation in wheel spacing are made to accommodate the different spacing between rows of particular crops. In addition, equipment is often temporarily attached to the frames of such tractors in a manner that can limit the clearance for the steerable wheels. Finally, the tire size itself is often changed to suit different tractive conditions. Thus, tractors are usually provided with means for limiting the pivotal movement of the steerable wheels. The need to limit pivotal movement has become increasingly important as the size of the front wheels on tractors have increased with the addition of mechanical front-wheel drive to many such tractors.
Prior art stops typically use a bolt stop to limit steering angle. In these stops, a bolt is threaded into a hole in one of the pivot members of the steering assembly. The bolt extends out of the hole on at least one side and contacts an abutment on an opposing pivot member to limit angular movement between pivot members. Adjustment of the steering angle is provided by turning the bolt in or out of the threaded connection. Different means of locking the bolt at a particular adjustment length are provided, such as a locknut on the bolt. One problem with this method is that a bolt, unless excessively large, may be inadequate to withstand the high compressive forces imposed by the steering system of the large vehicles. More significantly attaining the proper extension of the bolt to suit particular tire and wheel spacing combinations requires knowledge of the necessary bolt length or trial and error adjustment following each change to a new combination. Since a separate stop is usually used for each turning angle direction the stop adjustment must be performed twice for each change in wheel clearance.
Adjustable wheel stops using washers over the section of a bolt extended as a stop or movable blocks bolted to an axle are also known. With the washer system, a specified number of washers are placed over the bolt to set the clearance. Adding washers increases the compressive strength of the stop and prevents failure of the bolt. In the case of blocks, changing the position or thickness of the block sets the turning angle. While either the washer and bolt or block arrangement will increase the strength of the stop, both systems are inconvenient since the retaining bolts must be completely removed to add washers or change the blocks. Furthermore, in the case of washers or blocks of different thickness, the operator has additional loose pieces that must be stored when not in use.
Accordingly, it is an object of this invention to provide an adjustable steering stop that will be capable of handling the high steering loads transmitted to the steerable wheels of a vehicle.
It is a further object of this invention to provide a steering stop that is quickly adjustable to suit a number of specific turning angles.
A yet further objective of this invention is to avoid the use of loose pieces in an adjustable steering stop.